Method of making steel or alloy tubes.



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"team: JAY 10mm, or nLLwoon CITY, PENNSYLVANIA, assrenon To THE SHELBY STEEL TUBEGOMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF NEW JERSEY: 4

METHOD OF MAKING STEEL OR ALLOY TUBES. I

.No Drawing. 1

To all whom it may comm:

vthe operations of forming into cold drawn seamless tubes, shafting, and similar hollow or cylindrical bodies.

The object of this invention is to provide an improved method of treating the steel or alloy during its formation into cold drawn annular bodies such as seamless tubes.

In the making of such seamless tubes the heated billets or metal blanks are pierced at a temperature of from 1200 to 1300 degrees C. The piercing operation is performed with a loss intemperature of less than 100 degrees 0., and, unless the wall of the blank for cold drawingis comparatively thin, the later work in the rolling mill is so small as to have little or no efi'ect in breaking down the grain of the metal, so that at the beginning of the cold drawing operations the structure of the steel is coarsely crystalline. In existing 'methods used heretofore in makin such tubes, the billets, after being pierced, are reduced in cross section and wall thickness and increased in length in a rolling mill, usually immediately after the piercing operation and without reheating the pierced billet. The so-formed tubes after'being rolled are pickled, and then subjected to cold drawin-goperations to further reduce the wall thickness of the tubes and to form them" to the desired diameter, being annealed after each cold drawing operation by heating to a temperature of about 720 de recs (3., and thencooling, a temperature which does not affect the structure or alter the grain size of the steel. I have discovered that when such pierced billets or partly formed tubes are annealed at a temperature of from 900 to 950 degrees 0., or slightly above the upper critical point, the structure of the steel is changed and the coarse crystalline structure present before such annealing 'is modified, being refined'into a fine granular structure which structure is not afiected nor changed in the later cold drawing and annealing operations, the later an Specification of Letters Patent. Patented 0C1 17, 1911,

Application filed October 8, 1910. Serial No. 586,018.

nealings being always efi'ected by heating to a temperature ranging from 720 to-less than 900 .degrees C. V

When the material is to receive morethan three cold drawing operations to produce the required size it is desirable to repeat the anneal at the refining temperature to break up any micro flaws and prevent their extension in the futher cold working.

The advantages of my inventionwill be apparent to those skilled in the art. By subjecting the metal to the. 'heat treatment as above described,,the metal is refined and the coarse crystalline structure of the steel or alloy always present after the piercing,

operation is altered and changed into afine granular structure. The desired fine granular structure imparted to the metal by such heat treatment is maintained without substantial change during the subsequent cold drawing operatidn.

By treating the blanks for cold drawing in accordance withmy improved method, longitudinal sp itting of the tubes by rea son of the cold drawing operations and breakage heretofore caused in subjecting the tubes to the cold'straightening operations following the cold drawing steps, are reduced and practically eliminated and tubes of increased strength and superior quality are obtained. I

By seamless cold drawn tubes as used in the specification and claims, all hollow cold drawn articles are intended to be covered whether of cylindrical, square or other cross section.

Modifications 'in the steps of the process may be made within the scope of my invention as defined in the appended claims. The number of such steps may vary, depending upon the thickness of the wall in the pierced blank relative to that of the completed article, and other changes may be made. )7

I claim 1. In the manufacture of seamless cold drawn tubes and similar hollow bodies, the steps consisting in annealing the hollow blanks by heating above the upper critical point and then cooling and then subjecting the annealed blanks to a cold drawing operation.

f 2. In the manufacture of seamless cold drawn tubes and simi'larhollow bodies, the

steps consisting in annealing the hollow -low the upper retardation blanks by heating above the upper critical point and then cooling and thensubjecting the annealed blanks to the usual cold drawing operations, the drawn tubes being an 'nealed at a temperature not exceeding the upper critical point.

3. In the manufacture of seamless tubes and similar hollow bodies, the steps consisting in annealing hollow billets by cooling after heating above the upperretardation point and then alternately cold drawing and annealing the partly formed tubes in reducing the tubes to the desired wall thickness and diameter, the metal being heated to bepoint after the cold drawing operations.

4. The method of making seamless tubes and similar hollow bodies consisting in sub- 7 jecting hollow steel blanks to alternate cold drawing and annealing operations, heating the hollow blanks to above the-upper critical point :in-beginning the annealing operations and heating to temperatures less than the upper. critical point in subsequent annealing operations, repeating the heating operation to above the upper critical point, again cold drawing andannealing, and again annealing heating to below the upper critical point.

5. The method of making seamless tubes and similar hollow bodies consisting in subjecting hollow steel blanks to alternate cold drawing and annealing operations, heating the hollow blanks to 900 degrees C. in beginning the annealing operations and heating to temperatures less than 900 degrees C. in subsequent annealing operations, and repeating the heating operation to above the upper critical point as the final annealing M. E. NOLAN.

- operation.

In witness whereof, I have hereunto set my hand. 4

JERRY JAY DUNN.

Witnesses:

B. F. GooDRIoH, 

